A variety of litter boxes or waste disposal systems exists with a mechanism for removing animal's waste from a bed of particulate litter. These systems may be classified into several categories based on their construction and functions. For example, one type of system includes a stationary litter tray with a rake, basket or scoop which moves along a predetermined path inside the litter tray to collect animal's waste from the bed of particulate litter. Another type of system uses a rotary litter container with a sifting screen positioned inside the container for separating animal's waste from the particulate litter as the container is rotated about a horizontal axis. A third type of system uses a conveyer belt for removing a mixture of animal's waste and particulate litter from one end of the container while clean litter is added at the other end of the container.
An example of a litter box with an automatic rake-moving mechanism is described in the U.S. Pat. No. 4,574,735 entitled "Electronic Litter System" issued to Hohenstein. This system uses a rake which rotates about a vertical axis in the center of a circular litter container. An animal sensor in the form of a membrane switch is used for detecting the presence of an animal inside the container and a delay circuit is used for energizing an electric motor to rotate the rake at a predetermined time after the animal has left the container. A second sensor for sensing the amount of waste in the waste container is also provided.
One problem associated with Hohenstein's device is that the rake always remains inside the litter container in a position which can make it difficult for an animal to move around or walk over the bed of particulate litter. In 1987 the applicant solved this problem by using a rack-and-pinion mechanism for moving a rake into and out of the bed of particulate litter (U.S. patent application Ser. No. 080,472, abandoned). A prototype which was demonstrated to litter-box manufacturers in the U.S. in 1987 employs a rake which moves back and forth along two racks positioned on opposite sides of a rectangular litter tray. The racks are curved upwards at opposite ends to cause the rake to move downwards into the litter bed at one end of the litter tray and upwards out of the litter bed at the other end of the tray. The mechanism for moving the rake is also used for moving the lid of the waste compartment as the rake leaves or enters the waste compartment. A mechanism for opening and closing a waste bag inside the litter-box housing is also described in the applicant's abandoned application. This bag-closing mechanism may be used in combination with a mechanism for sealing a bag with the use of heat, adhesive, or any suitable type of fastener.
One serious problem associated with this type of waste-removing mechanism is that it can be dangerous to the animal if the system is made to operate in a fully automatic fashion with the use of animal sensors, especially since most types of sensors are known to malfunction or fail to work properly from time to time. Another problem associated with this type of waste-removing mechanism is its inability to remove very small pieces of waste from the particulate litter. If the spacings between the prongs of the rake are substantially smaller than 1/2 inch, the rake would tend to push the particulate litter along with animal's waste into the waste container even when the device is used with fine-grain clumpable litter. A similar problem arises when the system is used with medium-grain litter even if the spacings between the prongs of the rake are substantially larger than 1/2 inch.
Several similar waste disposal systems have since been introduced which use a rake or a scoop for collecting animal's waste from the bed of particulate litter. Examples of these systems are shown in U.S. Pat. No. 5,048,465 entitled "Self-Cleaning Kitty Litter Box" issued to Carlisi, U.S. Pat. No. 5,226,388 entitled "Automated Cat Litter Disposal System" issued to McDaniel, U.S. Pat. No. 5,267,530 entitled "Self-Cleaning Cat Litter Box" issued to Zamoyski, U.S. Pat. No. 5,477,812 entitled "Automated Self-Cleaning Litter Box for Cats" issued to Waters and U.S. Pat. No. 5,544,620 entitled "Self-Cleaning Cat Box" issued to Sarkissian. However, none of these systems provides a satisfactory solution to the problems mentioned above.
The second type of system uses a rotatable container with a sifting screen attached to the inside of the container for separating animal's waste from the particulate litter. Examples of these systems are found in U.S. Pat. No. 4,120,264 entitled "Sanitary Facility for Pets" issued to Carter and U.S. Pat. No. 5,662,066 entitled "Automatic Cat Litter Device and Method" issued to Reitz. This type of system do not work well with non-clumpable, non-absorbent litter since the liquid waste will tend to flow along the interior surface of the container as the latter is rotated. These systems can also produce a lot of dust when used with clumpable litter and cannot effectively remove pieces of waste or clumps which adhere to the inside surface of the container.
Another type of system employs a conveyer belt for supporting the bed of particulate litter and for removing a mixture of animal's waste and particulate litter from one end of the litter container while clean litter is added at the other end. Examples of these systems are described in U.S. Pat. No. 4,465,018 entitled "Pet Relief Station" issued to Mopper and U.S. Pat. No. 5,289,799 entitled "Automatic Pet Relief Station" issued to Wilson. Although these systems are believed to be safe for the animals, the mechanism for removing the waste from the litter can be complicated and difficult to clean.
SUMMARY OF THE PRESENT INVENTION
It is therefore an object of the present invention to provide an automatic waste removal system for animal with a safe waste-removing mechanism. Another object is to provide a waste-removing mechanism which is capable of removing substantially smaller pieces of waste from the bed of particulate litter. A further object of the present invention is to provide an automatic waste disposal system which is suitable for use with medium-grained non-absorbent litter as well as fine-grained clumpable litter.
These and other objects are achieved in accordance with the present invention by providing a stationary housing having an area for holding a bed of particulate litter. For illustrative purposes, the bed of particulate litter is arbitrarily defined by multiple contiguous sections. Each section may be separately and independently cleaned or processed by the waste-removing mechanism.
The present invention employs a scoop having a cup-shaped cross section with perforations for separating and removing animal's waste from the bed of particulate litter. The scoop is coupled to an electric motor which is securely positioned in the housing. In the preferred embodiment an electric motor provides the driving force for the lateral and pivotal movement of the scoop relative to the stationary housing. This movement selectively positions the scoop above any predetermined section of the litter bed for capturing animal's waste from that section. The scoop is pivoted into the litter bed and moved laterally by a small distance to collect a mixture of animal's waste and particulate litter. It is then pivoted out of the litter bed and moved laterally towards one end of the litter tray while the particulate litter inside the scoop is allowed to fall through the perforations into the litter tray. Further pivoting of the scoop causes animal's waste to fall into the waste container. The waste-removing process is then repeated to remove animal's waste from the remaining sections of the litter bed until all of the sections have been cleaned or processed.
The second embodiment of the present invention employs a different mechanism for pivoting the scoop. This mechanism includes a plurality of tracks or guide rails positioned adjacent to the litter tray to cause the scoop to rotate or pivot about its axis of rotation as the latter is moved laterally.
Two types of retractable partitions are provided for making the waste-removing mechanism inaccessible to the animal during its automatic operation. Consequently these retractable partitions can make it physically impossible for the animal to get injured by the waste-removing mechanism. For the purpose of illustration, these retractable partitions are shown in separated embodiments although either of them may be used in combination with the waste-removing mechanism shown in the first or the second embodiment.